Vehicle acceleration/deceleration warning system

ABSTRACT

A compound pendulum allows light to impinge upon properly positioned acceleration or deceleration photocells to vary the resistance of the photocells in accordance with the angular displacement of the pendulum; the amount and direction of angular displacement of the pendulum is dependent on the amount of acceleration or deceleration of the vehicle. Variation of the deceleration photocell resistance varies the frequency of an oscillator circuit to alternately flash a pair of warning lights at a frequency dependent on the rate of deceleration of the vehicle. The acceleration photocell must receive maximum illumination (a threshold value) to actuate a light for warning of a minimum rate of acceleration of the vehicle. A manual switch allows a high flash rate of alternate warning lights to be controlled by the operator of the vehicle. An audio generator produces a continuous tone for acceleration and an interrupted tone for deceleration, the frequency of interruption corresponding to the flash rate of the deceleration warning lights. The system is an aid in preventing rear end collisions and will save gasoline if properly used.

LIST OF THE PRIOR ART

U.S. Pat. No. 4,107,647, Aug. 15, 1979--Yoshino

U.S. Pat. No. 3,567,956, Mar. 2, 1971--McNiel

U.S. Pat. No. 3,089,129, May 7, 1963--Nassikas et al.

U.S. Pat. No. 2,734,105, Feb. 7, 1956--Perry

U.S. Pat. No. 3,559,164, Jan. 26, 1971--Bancroft et al.

U.S. Pat. No. 3,787,808, Jan. 22, 1974--Knopf

DISCUSSION OF THE PRIOR ART

A review of the prior art in this field shows various schemes forsensing and displaying the state of deceleration of a vehicle. Thevarious types of sensors used include: pendulums, spring loaded massesoperating horizontally, mercury switches with single and multiplecontacts, switches on brakes, pressure sensors and switches in hydraulicbrake systems, manifold pressure sensors, sensors on moving shafts,change in drive power sensors, metallic balls on inclined resistivetracks, centrifugal switches, rotating magnets, various linkage systemson carburetor throttles and brake pedals, as well as combinations ofthese types of sensors.

Prior art displays include: simple flashing lights, momentary flashingbrake lights, flashing of a single turn indicator, intensity variablelights, different colored lights, illuminating display panels, and highintensity flash and photoflash lamps.

Prior art means used for electrically actuating these displays are:thermal-type flashers of constant flash rates, flashers sensitive tothermal changes for variable rates, rotating magnets, carbon piles,potentiometers, step function RC electrical oscillators, and frequencyand digital processing devices.

Sensors measuring pressure in brake systems can have gross errorsdepending upon the coefficient of friction between the brake linings (orpads) and the surface contacting these elements. Variations in driverhabits and in these surfaces (when wear has started) are two otherconsiderations. Presently used brake light display systems are simpleon-off indicators the actuation of which required only a fraction of themaximum total pressure applied. Reliability is quite high, and theseuseful displays will probably continue to be used (in addition to anydeceleration warning display).

Sensors taking information from rotating parts are not viable when thebraking system has locked the wheels and subsequent drive shaft, thusgiving a zero output when further deceleration of the vehicle is stilltaking place. Horizontal spring loaded masses can be affected adverselywith temperature variations, changes in friction coefficients, wet ordry conditions, and mechanical mounting changes due to road shocks orthe like.

Mercury switches, when sealed, afford an excellent means of switching.The housing of these switches requires an insulating material which isusually glass (since it is economical, easy to use, and the leads orcontacts can be sealed) and requires special care in mounting.Mechanical shock can present a problem since the main body of themercury can break up into small globules which can hang up on contactsor other irregularities in the housing.

All of the pendulums used in the devices of the prior art make use ofswitch contacts or potentiometers which are mechanical and are actuatedby a short extension of the pendulum near the pivot point. A switch, inmost cases, requires a firm solid contact and a wiping action to stay infaultless operation. A potentiometer also requires mechanical contact(with sometimes even greater friction than that needed for the switchwiping action) with the wire or composition of the resistive element.This mechanical loading requires that the pendulum be made long enough,with enough weight at the bottom end, to overcome this mechanical dragand still respond to changes. If the pendulum is shortened to meet asize requirement, more bottom-end weight will be needed. With a largerand heavier pendulum, the support and bearing at the pivot point must bemade strong enough to support the pendulum and allow it to swing, whilestill restraining it from excessive side motion. The bar forming thelength of the pendulum has to meet more rigorous mechanical requirementsto accommodate this weight, thus presenting further problems. Mountingit in today's vehicle (where space is always at a premium) and supplyingan appropriate bulk head, bracket, or brace in the vehicle to supportand retain the assembly under road conditions is one such problem.

BRIEF SUMMARY OF THE INVENTION

This invention concerns an acceleration and deceleration warning devicefor motor vehicles. The device performs at least two very usefulfunctions: (1) warning a trailing vehicle of deceleration in order toaid in the prevention of rear end collisions, and (2) warning theoperator of the vehicle of possible bad habits in starting and stoppinga vehicle, to thus allow the operator to improve these habits and savein gas, brakes, tires, and possible well being. This inventionincorporates the use of an alternating flashing lights, the flash rateof these lights being proporational to the amount of deceleration of thevehicle. When a vehicle has stopped abruptly, or a collision hasoccurred, a high rate of flashing of the lights continues until thedevice is reset manually. Drivers of following vehicles are therebyalerted to slow down, stop, or take whatever action is required toprevent an accident (or to become part of an existing accident). Thisdevice can be set to reasonable threshold levels for deceleration andaccelerations. If these threshold levels are exceeded, a pair of lightswithin sight of the driver will flash at a rate proportional to theamount of deceleration that is experienced and in unison with a pair ofwarning lights on the outside rear of the vehicle. An audible generatoris also incorporated into the device, such that the tone is interruptedor beeped at the rate of flash of one of the alternating, flashinglights. This indicates to the driver that the vehicle deceleration wastoo fast and more braking was required than was necessary. With practicein the use of the device, the driver of the vehicle should be able torealize a savings in the wasted gasoline and wear and tear on the brakesurfaces, by gradually applying the brakes for an anticipated stop.

When the driver exceeds the threshold of accerelation, a light and tonein continuous manner will be activated as an indication that, except ina case of emergency, fuel has been wasted on an amount of accelerationthat is not necessary. A conscientious driver will, after someexperience, improve his or her driving habits.

When the vehicle becomes stalled or immobile, a manual switch can beused to activate the flashing lights to alert oncoming vehicle driversof the danger.

The alternating flashing lights on the rear of the vehicle should beplaced within the upper 1/4 of the overall height of the vehicle, makingthem visible to the immediate trailing vehicle as well as other trailingvehicles. The lights should also be spaced horizontally as far apart aspossible, with the spacing between the lights standardized for allvehicles; this standardized spacing would allow drivers of trailingvehicles to develop a sense of distance from the flashing lights.

This device will operate in any road vehicle and measures only the rateof positive or negative acceleration. A heavily loaded truck willrequire a much longer braking distance than a passenger vehicle, as wellas more time to accelerate in a positive direction; the device can stillbe used on these heavy vehicles and will measure the acceleration thesame as it would on a light, compact, vehicle experiencing the sameamount of acceleration. Acceleration is defined as a time ratio ofchange of velocity and is irrespective of the size and weight of thevehicle or other object. This device is an improvement in vehicle safetyand does not replace brake lights. Brake lights are only an indicationthat the brakes have been applied; this device operates independently ofthe brakes, except that it measures the effect of the brakes when theyare applied. When a prudent driver of a vehicle using this device slowsdown or comes to a stop, the brake lights will go on, but the warningsystem will not be activated. Only when the deceleration or accelerationlimits are exceeded will the system indicate a response with the warninglights; that response is completely automatic and not part of any othersystem of the vehicle except the electrical system which supplies powerto the warning device.

The pendulum used in the instant invention is quite small, 42millimeters (mm) or approximately 1.7 inches, in length from the pivotpoint to the bottom end. This pendulum is not required to do anymechanical work except to move in accordance with changes in vehiclevelocity. Prototype pendulums have been fabricated from small rigidtubes or channel sections of brass in the order of 4 mm. square. Twopermanent magnets are placed, with poles aiding, within the channelsections. These magnets are approximately 0.125 inches square and 0.755inches long (thus, allowing a snug fit into the pendulum section), andare fastened permanently into the section. Each magnet weighsapproximately 1.5 grams, or a total of 3 grams for the pair of magnets,with the entire assembled pendulum weighing a total of 4 grams. Thegreatest mass obviously is in the magnets, the weight being distributedover the entire length of the pendulum; and the center of gravity of thecompleted pendulum is approximately 20 mm below the point of suspension.The completed pendulum unit, being light of weight, is quite easy tohandle mechanically from the standpoint of suspension of the mass duringdeceleration or acceleration. The means of suspension is rather simpleand novel. It makes use of a common machine screw (2-56) as the fixedsuspension point, and two like-sized nuts are threaded onto the screw oneither side of the pendulum. The pendulum then swings on the threads ofthe screw. A dry lubricant on these threads allows a very free swingingpendulum and provides and exceptionally free, smooth suspension system(with built-in side restraint offered by the spaced nuts threaded oneither side). This suspension feature is also useful and economical inassembling the unit, since it can be adjusted toward or away from a backmounting plate by the nut and screw arrangement. The threaded screwpivot works well as a bearing for the pendulum and provides lateralstability, all in an economical way and with easy assembly andadjustment.

This pendulum and associated support base, in production quantities,permits injection molding techniques in which the threaded portion couldbe molded to the pendulum; molding materials offering excellent strengthand low friction characteristics are readily available. The magnetscontained within the pendulum section perform three functions. In theorder of use, these functions are: (1) to provide damping on pendulummovement by exerting a magneto-motive force (mmf) between the pendulumand a shaped, soft steel, thin plate mounted on the back support andparallel to the plane in which the pendulum swings: (2) to close a reedrelay switch (which sets the threshold for the low deceleration value)at a predetermined number of degrees from vertical; and (3) to lock thependulum to a stop when it has exceeded the high limit of deceleration,as might occur in an emergency stop or crash. This allows warningindicators to continue in operation until the vehicle is in a safeposition and a manual reset button is actuated. This reset push buttonoperates against a canted section of the pendulum, extending upward fromthe suspension point at an angle of 45° and allows release of thependulum after deceleration has been high enough in value to swing thependulum an angle of 45° into contact with a stop plate. The oppositeend (bottom) of the pendulum is also functional, having a reflectivesurface at an angle to the pendulum section for reflection of light froma light source onto a photocell when a predetermined amount ofacceleration has taken place.

Prototypes of the entire system have been built and packaged on asingle-sided printed circuit card of 31/2 inches by 4 inches with athickness, including the projection of all parts from the card, of lessthan one inch. This total package of 14 cubic inches, without aprotective cover, weighs less than 4 ounces. The light weight and sizeof the package allows ease of mounting to a dash board and requires asmall amount of space. A reset push button and small warning lights(corresponding to the warning lights on the outside of the vehicle) aremounted on the front panel of the unit within easy access and view ofthe operator of the vehicle. Various adjustable bracket mounting meanscould be utilized to ensure proper positioning of the unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the warning circuit.

FIG. 2 is a prospective view of the pendulum assembly.

FIG. 3 schematically illustrates the angular relationships between thependulum, light source, and photocells of one embodiment of theinvention.

FIG. 4 is a perspective view of an alternate embodiment of the pendulumassembly of the invention.

FIG. 5 discloses an alternate embodiment of the push button resetassembly for the pendulum assembly.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 2, a mounting base 1 may be molded plastic, or thelike material, for production quantities; a piece of glass phenolicboard was used for the prototype. Mounted in fixed positions on base 1are: push button bracket 103, nut 7, threaded support rod 4, reed switch5, stop plate 8, damping plate 9, light source 12, and photocells 13 and14. The mounting means for these various parts (i.e., push-buttonbracket 103) may be molded as a part of mounting base 1 duringmanufacture thereof.

Threaded rod 4 is the pivotal suspension support for a pendulum 2. Rod4, as well as nuts 3 on each side of pendulum 2, are composed of amagnetic material; thus providing magnetic damping for the pendulum andpart of a magnetic path (which also includes screw 6) to reed switch 5.Screw 6, of magnetic material, is for adjustment of the coupling of themagnetic field of pendulum magnet(s) 10 to thereby set the closing ordeceleration threshold of reed switch 5. Closing of reed switch 5completes the ground to the emitter of an oscillator circuit driver,thus allowing variation of the oscillator frequency (nominally 0.25Hz-5.0 Hz) in proportion to the amount of illumination of photocell 13,for deceleration levels greater than the deceleration threshold level.By using screw 6, the tolerances of reed switch 5 and the pendulummagnet(s) 10 may be loose (as much as plus or minus 30%) to allow formanufacturing economy. Angular displacement of pendulum 2 (left-ward asseen in FIG. 1) actuates the closing of reed switch 5 by the magnet(s)10 which are disposed within the pendulum 2. Mechanical stop plate 8 isdisplaced at a left-ward angular displacement of 45° from the verticalposition of pendulum 2. Stop 8 is made of a high permeability softmagnetic material; when the pendulum reaches an angular displacement ofover 30° (representing a deceleration of 16.1 feet per second, persecond or 0.5 "g"), the magnet(s) 10 located in pendulum 2 pull thependulum to the stop 8 and hold it in this position until it is releasedby a manual reset push-button assembly 100. With the pendulum heldagainst stop 8, reed switch 5 is held closed with an even greatermagnetic force to thereby prevent any mechanical shock experienced bythe automobile from opening the contacts. Damping plate 9 is a flatstrip of magnetic material, with high permeability and low retentivity,for providing mechanical damping to pendulum 2 which pivots in closeproximity to damping plate 9; this is due to the magnetic field createdby the permanent magnet(s) 10 located within pendulum 2. As can be seenfrom the figures, the damping action is increased as the left-wardangular displacement of pendulum 2 increases; a small magnetic path alsois provided by damping plate 9 for activating reed switch 5. The leftend of damping plate 9 is physically separated from stop 8, thusallowing the magnetic force to be increased slightly when the pendulumis held at stop member 8. Push-button assembly 100 includes button 101attached to plastic rod 104 and inserted into a plastic or non-magneticbracket 103. A spring 102 urges plastic rod 104 to a retracted position(to the right in FIG. 1), such that a canted extension 2' of pendulum 2almost engages rod 104 when the pendulum 2 is held against stop 8 asindicated by the phantom line position 2a of FIG. 1. By depressingbutton 101, plastic rod 104 is urged into contact with extension 2' ofpendulum 2 to disengage pendulum 2 from stop 8; spring 102 returns rod104 to the position of FIG. 1. Located at the bottom end of pendulum 2is a flat plate or section 11 surfaced at the proper angle of 42' (asbest seen in FIG. 3. The outer surface of plate 11 is reflective to alight source 12 (7° below horizontal) and is dimensioned and positionedto reflect the light from light source 12 in a manner to be described.Light source 12 may be an LED which emits a red beam of light. Anyradiant source of energy could be used with compatible light sensors. Inthis embodiment, photocells 13 and 14 are arranged as shown in thefigures. The electrical resistances of these photocells 13 and 14 ishigh when they are not illuminated; the resistance value of each isdecreased with an increase of illumination up to a saturation point. Ascan be seen from the figures, the illumination of photocell 13 varies asthe left-ward angular displacement of pendulum 2 varies fromapproximately 8° to 221/2° (the 8° value is the deceleration threshold).Left-ward angular displacement of pendulum 2 occurs during deceleration,with right-ward angular displacement of pendulum 2 occuring duringacceleration the amount of angular displacement is proportional to theamount of deceleration or acceleration. Photocell 14 is for sensing athreshold value of acceleration. Photocell 14 is fully illuminated aftera very small right-ward angular displacement of the pendulum and willremain fully illuminated as long as the acceleration is a minimum valueequivalent to 8° of right-ward angular displacement of pendulum 2. This8° pendulum swing represents an initial value of acceleration ofapproximately 4.5 feet per second, per second.

FIG. 1 also discloses the circuitry necessary for actuation of thevarious warning signals. Integrated circuit (IC) 22 contains a variableoscillator and subsequent driver; this is an integrated circuit usedcommonly in the industry and classified as CA3094. IC 22 is adifferential input power control amplifier, consisting of a pair ofoperational amplifiers coupled to an internal Darlington coupled powertransistor capable of supplying a driving current of up to 100milliamps. FIG. 1 discloses a top view of the pin connections of IC 22.Pins 2 and 3 are the inputs to the operational amplifiers. Pin 8 is thecollector output of the power amplifier (resistor 20 is the loadresistor connected between pin 8 and B+) and drives subsequenttransistors 26 and 28, the output of pin 8 being a square wave. Pin 6 ofIC 22 is the emitter of the driver and is returned to ground throughresistor 23 when reed switch 5 is closed or when double-pole,single-throw switch 46 is closed, resistor 23 removes the ground returnfor the amplifier when the pendulum 2 is in a vertical, i.e. rest,position. Resistor 45 is a current limiting resistor for light source12. Resistors 15, 16 and 17 fix the bias of one of the internalamplifiers of IC 22, with resistor 17 selected to adjust the symmetry ofthe square wave oscillator output. Resistor 18, in series with thevariable resistance of photocell 13, forms the RC time constant for theoscillator in conjunction with capacitor 19. Resistor 21, connectedbetween pin 5 of IC 22 and B+, controls the gain of the differentialamplifiers, and is selected to make the input impedance of thedifferential amplifiers high. Transistors 26 and 33 are PNP powertransistors for driving respective warning lights 39,36. These powertransistors are rated at 7 amps of continuous collector current to allowgenerous derating for warning lights 39, 36, which are of the typegenerally used as vehicle rear indicators. A medium power NPN transistor28 operates as a phase inverter such that transistor 33 is "on" whentransistor 26 is "off", and vice versa, according to the square wavefrequency. For respective transistor 26, 28, and 33, resistors 25, 29,and 32 are base-emitter biasing resistors, and resistors 24, 27, and 31are drive/isolation resistors. Resistors 47 is shunted across photocell13 when manual switch 46 is closed; the value of resistor 47 issubstantially equal to the maximum illumination resistance value ofphotocell 13. Thus, by closing switch 46, warning indicators 39, 36 arealternately flashed at a high rate (as in maximum deceleration); thisprovides for a trouble light arrangement much like that normallyprovided on automobiles, except that the warning lights of the instantinvention are alternated. A PNP-type power transistor 41 is biased onwhen the minimum threshold of acceleration has been reached, such thatmaximum illumination reaches photocell 14 to lower the resistance valuethereof. The resistance value of photocell 14, together with resistor40, forms a voltage divider network to establish biasing voltage oftransistor 41. Transistor 41 is used to drive acceleration indicator 44located on the exterior of the vehicle. Audio generator 53 is driven bytransistor 41 to provide a constant tone during acceleration; transistor33 drives audio generator 53 during deceleration to provide aninterrupted tone. Shunted across indicators 39, 36 and 44 are respectivetell-tale lights (such as LEDS) 38, 35 and 43 located within view of theoperator of the vehicle.

FIG. 3 discloses the angular relationship between pendulum 2, lightsource 12, and photocells 13 and 14. The tip of pendulum 2 describes anarc as shown. Reference line V indicates a vertical, and reference lineH represents a horizontal tangent to the arc at the point ofintersection with reference line V. The arc has degree markingsincreasing left-ward and right-ward from the vertical reference line Vfor ease of understanding the invention. The right-hand side of pendulum2 (as seen in FIG. 2) lies along reference line V when the pendulum isat rest and in the vertical position. Pendulum 2 is limited inright-ward angular displacement by abutment with photocell 13 and inleft-ward displacement by stop plate 8. Reference line M indicates themajor axes of pendulum 2; this major axes M crosses the 8 degree mark onthe arc when the pendulum has been displaced by 10 degrees right-ward,(at which time pendulum 2 abutts photocell 13). In the decelerationmode, the trailing edge of the pendulum is defining the aperture. As canbe seen from the figure, this 10 degree swing of pendulum 2 providesmaximum illumination of photocell 14 by the reflected light from lightsource 12. Maximum illumination of photocell 14 is the threshold valueof acceleration warning. Of course, any greater acceleration, causingpendulum 2 to continue to abut photocell 13, continues to give maximumillumination to photocell 14. The direction of travel of the vehicle onwhich the instant invention is mounted is indicated by arrow 300. As canbe seen from figure 3, increased deceleration of the vehicle causesincreased left-ward displacement of pendulum 2 thus allowing more light(indicated generally at 301) from light source 12 to impinge uponphotocell 13; this variation in the amount of light reaching photocell13 ranges from no light reaching photocell 13 for any right-ward swingof pendulum 2 from vertical, to maximum illumination of photocell 13during any left-ward angular displacement of pendulum 2 which is greaterthan approximately 22.5 degrees. Therefore, the height of a lightaperture is defined by a perpendicular from the point on the arc atwhich the tip is located. For instance, when the tip of pendulum 2 is at20° the height of the aperture is indicated as line BC₁. The height ofthe aperture is a direct function of θ which, in turn, is a function ofthe linear acceleration of the vehicle.

As previously stated, the amount of light impinging upon photocell 13from light source 12 varies the resistance of photocell 13 to thusinfluence the frequency of the oscillator circuit and vary the rate offlashing of alternate deceleration warning signals 39, 36. In theacceleration mode, no acceleration indication is given until thependulum has been displaced right-ward by an amount of 10° or greater.

FIG. 3 shows the radiant energy beam displaced by 7 degrees from thehorizontal. With this displacement the aperture height of the beam belowthe pendulum tip is equal to a line BC₁. Lines BC and BC₁ are drawn fromthe 20 degree displacement angle only for the sake of visual clarity.Line BC₁ from any position on the arc of the pendulum determines theaperture height and can be determined by the sin of angle θ plus 7degrees for the added angle, and the aperture increasing with thedisplacement angle of the pendulum. The aperture formed by BC₁ is largerthan an aperture formed by line BC, which would be formed if the radiantenergy beam were in a horizontal plane, especially at small angles ofdisplacement. The 7 degree angle was selected as a result of thefollowing arbitrary limits and the selection of electronic components.The low limit or threshold of deceleration which will activate thewarning lights were chosen to be four and one half feet per second, persecond, which is equal to a g value of 0.14 and a pendulum displacementof 8 degrees. The maximum flash rate is reached when the decelerationreaches 12 feet per second, this represents a g value of 0.4 and adisplacement angle of 221/2 degrees. Unrestrained objects in a vehicleincluding the occupants on seats, will start to slide or move forwardwith a deceleration level of 0.5 gs. So to insure more safety the highlimit of deceleration was set at 0.4 gs to be below the 0.5 g level.These arbitrary limits resulted in an aperture height determined by BCat the 8 degree displacement position which, was too small to properlyactivate sensor 13. The energy source is a L E D with a limited amountof light. Displacing the energy beam by 7 degrees provide an apertureformed by BC₁ of acceptable size. In fact, the aperture of 8 degrees,i.e. line BC₁, is 2.73 times higher than the length of B C. At apendulum displacement angle of 221/2 degrees the ratio of B C₁ over B Cis 1.6, which gives an aperture ratio from 8 to 221/2 degrees ofapproximately 4.6, which is suitable in this case, for a cadmiumselenide sensor, packaged in a standard TO-5 semiconductor can. The 7degree angle dictates that the reflective surface at the tip of thependulum is set at 42 degrees with respect to the axis of the pendulum.This provides maximum illumination on sensor 14 when the sensitivesurface of the sensor is parallel to H and the pendulum is in theextreme right position representing the threshold of the accelerationmode.

FIG. 4 illustrates an alternate embodiment in which a flat sector typependulum 200 is used; the parts of the alternate embodiment that are thesame as those of FIG. 2 have like reference numerals. Light source 212and photocell 213 correspond to light source 12 and photocell 13 of FIG.2 for indication of deceleration. Photocell 214 corresponds to photocell14 of FIG. 2; however, the light source for this photocell 214 isindicated by light source 51. The flat sector type pendulum 200 hasapertures 52 and 50 therein and permanent magnets 48 and 49 mountedthereon. Permanent magnets 48 and 49 are used in much the same manner asmagnets 300 of FIG. 2. For instance, permanent magnet 48 is used toactuate reed switch 5, and permanent magnet 49 is used for mechanicaldamping of pendulum 200 as well as for a means of attracting and holdingthe pendulum 200 to stop 8 when the pendulum is displaced toapproximately 40°.

In the deceleration mode, pendulum 200 swings left-ward, and lightsource 212 is aligned with light source 213 through aperture 50 during aportion of the swing of pendulum 200. The amount of illuminationreaching photocell 13 is controlled by the shape of aperture 50 suchthat a small amount of light reaches photocell 213 for an 8° left-wardangular displacement, the illumination gradually increasing with thesize of aperture 50 up to approximately 22° at left-ward angulardisplacement. As can be seen from the shape of aperture 50, the amountof illumination reaching photocell 213 is constant from approximately22° up to 45°, at which time there is no further left-ward angulardisplacement of pendulum 200.

During the acceleration mode, photocell 214 will be fully illuminated(to the threshold level for actuating the acceleration indicator) whenpendulum 200 has been angularly displaced right-ward by approximately8°, such that aperture 52 allows full illumination of photocell 214 bylight source 51. A stop (not shown) prevents the pendulum 200 fromswinging further than the acceleration threshold value of 8°, such thatan acceleration that would cause a greater swing by the pendulum 200continues to allow aperture 52 to be aligned so that maximumillumination is on photocell 214 from light source 51. The selection ofthe acceleration and deceleration values, resulting in specific angularlocation of the apertures, is not limited to these values and can bedesigned to meet any specific values.

FIG. 5 discloses an alternate embodiment of a push buttom reset assembly400. Assembly 400 comprises a bracket 403 pivotally supporting a latch408 on a pivot rod 411; a spring (not shown) is concentric upon rod 411to bias latch 408 in the counterclockwise direction. Push button resetassembly 400 is shown in the relaxed position, in which positionpendulum 2 is latched when it is in the phantom line position of 2a. Theassembly 400 also includes a push button 401, a return spring 402, acollar 407 for abutting the bracket 403 to limit the return of pushbutton 401 and a latch actuating rod 404. Rod 404 has an angled portion405 to cooperate with angled portion 409 of latch 408. With pendulum 2in the latched position as shown in the phantom line position of 2a,pushing of push button 401 against the bias of spring 402 causes slantedportion 405 to engage slanted portion 409 of latch 408, thereby causinglatch 408 to rotate in a clockwise direction such that latch portion 410is no longer in contact with canted extension 2' of pendulum 2. Furtherdepression of push button 401 causes reset extension 406 of rod 404 toengage the canted portion of the pendulum 2 to release pendulum 2 fromstop plate 8.

The operation of any simple inertial device used in a vehicle will besensitive to any inclines (positive or negative) of the highway on whichthe vehicle travels. On most interstate highways and other modern roads,basically for safety reasons, the positive and negative grades (uphilland downhill) are limited to 5% in the mountainous areas, 3% in therural country, and are substantially flat otherwise. Some 8° gradesstill exist, but these are rare. The grade, given in percent, means thatthe road rises or falls from a horizontal reference line over a givennumber of feet. For instance, if the road rises or falls 25 feet over alength of 500 feet, it will go up or down 5% in grade. The actual angleformed by this amount of rise would be 2.8°. The average angle on an 8°grade would be 4.5°. When using the device described in this applicationon a grade of 5%, a vehicle traveling at constant velocity willexperience a pendulum bias of 2.8°.

When the vehicle is on a positive (5%, or 2.8° ) grade, the pendulumwill be biased backward toward the acceleration mode. With an additional5.2° of pendulum displacement in that direction, the accelerationindicators would be actuated (for an 8° acceleration threshold). Toactuate the deceleration indicators while traveling on this positivegrade, a deceleration mode displacement of 10.8° would be necessary(when the deceleration threshold is set to 8° ). When the vehicle is ona negative (5% of 2.8° ) grade, the reverse action will take place andthe pendulum will be biased 2.8° toward the deceleration mode. In bothsituations, the vehicle must be at a constant velocity as provided bycruise control. This type of control is not yet standard equipment onvehicles; a great many more vehicles are without it than are with it.Practically all drivers without cruise control unconsciously slow downwhen going uphill and unconsciously accelerate when going downhill.These two reactions tend to counteract the displacement of the pendulumand restore it toward the vertical. On the downhill side, the addedacceleration may even go the other way and bias the pendulum in theopposite direction. When the pendulum going down a 5% grade has todecelerate rapidly (or stop), the warning indicators will be activatedat a lower acceleration rate; since a 5% grade biases the pendulum to2.8°, an additional displacement of 5.2° will activate the warningindicators. Therefore, a total displacement of 8° will occur with adeceleration of slightly less than 3 feet per second, per second. Afollowing vehicle, due to this same grade, will take a longer distanceto slow down or brake to a stop. The braking distance that is requiredincreases on a negative grade and decreases on a positive grade, inproportion to the angle or rate of the incline. The instant inventionprovides a warning of deceleration which will alert the driver of thefollowing vehicle and will provide additional time (and thereforedistance) in which to accomplish a more rapid deceleration or stop. Thereverse is also true for a positive grade, since the braking distance isless. The fact that the pendulum bias changes due to these grades doesnot detract from the system when operating with two or more cars. Theeffect is compensated for in the action of the vehicles as far as anoperational safety device is concerned.

What is claimed is:
 1. An electronic acceleration and decelerationwarning system for a vehicle comprising:(a) a radiant energy sourcemeans for supplying radiant energy to first and second radiant energysensor means, said first radiant energy sensor means having resistancewhich is variable in proportion to the amount of radiant energyreceived; (b) a pendulum adapted to control the amount of radiant energyreceived by said radiant energy sensor means from said radiant energysource means in response to angular displacement of said pendulum arounda pivot point; (c) an oscillator circuit having a variable frequencyoutput signal; (d) a deceleration threshold switch means for switchingon the output signal of said oscillator circuit in response to a minimumangular displacement of said pendulum in one direction; (e) first andsecond alternately flashing deceleration warning lights having theirrates of flashing dependent upon the frequency of said oscillator outputsignal when said oscillator output signal is switched on; and (f) anacceleration threshold switch means for turning on an accelerationwarning signal in response to a minimum angular displacement of saidpendulum in a second direction.
 2. An apparatus as in claim 1, in whichsaid pendulum includes:(a) a reflector means, at an angle to the majoraxis of said pendulum, for reflecting all of said radiant energy awayfrom said first sensor means over a first portion of the angulardisplacement of said pendulum and for controlling the amount of saidradiant energy away to said first sensor means over a second portion ofthe angular displacement of said pendulum, whereby the amount of radiantenergy received directly by said first sensor means is a function of thedeceleration of the vehicle.
 3. An apparatus as in claim 2, in whichsaid second sensor means is disposed relative to said radiant energysource and to said pendulum to receive a threshold value of reflectedradiant energy from said radiant energy source when said pendulum hasswung to said minimum angular displacement in said second direction. 4.An apparatus as in claim 1, in which said pendulum includes a magnetmeans for actuating said deceleration threshold switch means.
 5. Anapparatus as in claim 1, in which said pendulum includes a magnet meanscooperating with a damping means to retard the angular motion of saidpendulum.
 6. An apparatus as in claim 1, in which said decelerationthreshold switch means is adjustable to vary the threshold value.
 7. Anapparatus as in claim 1, further comprising a stop means for saidpendulum for stopping and retaining said pendulum at a particulardeceleration displacement angle, said pendulum including a cantedportion for cooperation with a reset means for release of said pendulumfrom said stop means.
 8. An apparatus as in claim 1, further comprisingan audio tone generator adapted to produce a continuous tone inconjunction with said acceleration warning signal and an intermittenttone in conjunction with one of said deceleration warning lights.
 9. Anapparatus as in claim 1, further comprising manual switch means forturning on said oscillator output signal at the discretion of the driverof the vehicle.
 10. An apparatus as in claim 1, in which said first andsecond warning lights are spaced horizontally on the rear of saidvehicle and operate in an alternate flashing manner, the rate offlashing being proportional to the deceleration of said vehicle.
 11. Anapparatus as in claim 1, in which a threaded screw serves as said pivotfor said pendulum.
 12. An apparatus as in claim 1, in which the positionof said first sensor and said source is canted to obtain the optimumminimum illumination and the proper ratio of apertures.
 13. Apparatus asin claim 1, wherein said first and second warning lights are operativelyconnected to indicating means within the vehicle to indicate theoperation of said warning lights to the driver of the vehicle.
 14. Anapparatus as in claim 1, further including means for restraining themovement of said pendulum at a fixed point after said pendulum hasreached a given angle of displacement.